Ceramic hair care heating element

ABSTRACT

There is provided a heating element for a hair styling device, including an electrically insulating inner ceramic layer, an electrically conductive resistive heating layer disposed on and in contact with the inner layer, and an electrically insulating outer ceramic layer disposed on and in contact with the resistive heating layer. There is also provided a method for manufacturing the heating element. There is further provided a hair setting device for curling hair including the heating element a cylindrical barrel surrounding the heating element.

CROSS-REFERENCE TO RELATED APPLICATIONS

The present application is claiming priority of Chinese Patent Application No. 200520133523.X, filed on Nov. 25, 2005, the content of which is herein incorporated by reference.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to home appliances involving electric heating, and more particularly, to hair care appliances having heating elements.

2. Description of the Related Art

Commonly used hair curlers or hair setters generally employ cylindrical heating elements that contact hair by wrapping hair around the heating element to achieve a desired curling effect. Typical hair curling systems may include a hand-held curling iron featuring a handle, a cylindrical heating element, and an attachment to clamp the hair in place about the heating element. Other systems include a plurality of individual heat rollers that are docked in a power-supply unit and heated prior to application to hair.

FIGS. 1A and 1B illustrate prior art hair curlers typically used in systems described above. In a first example, FIG. 1A shows a rope heater 100 for a curling iron. Rope heater 100 includes a glass rope 105 and a resistive wire heater 110, which is electrically and removably connected to a power source via connectors 115. In the complete curling iron, rope heater is fit into a conductive sleeve, such as an aluminum sleeve, for use. In a second example, FIG. 1B shows a curling iron 120 that includes a positive temperature coefficient (PTC) heating element 125 surrounded by a thermally conductive outer layer 130. A die-cast piece 135 is provided between heating element 125 and outer layer 130 to facilitate heat transmission to outer layer 130.

The above-mentioned technological approaches utilize a conductive wire or plate that contacts or is proximate to an outer barrel to heat the outer barrel. These configurations, in which there is little or no direct contact between the conductive element and the outer barrel, possess numerous disadvantages, such as extended heating time and uneven heating.

SUMMARY OF THE INVENTION

It is an object of the present invention to provide hair setting and curling devices and systems that feature a quicker heating time than prior art systems.

It is another object of the present invention to provide hair setting and curling devices that provide even heating of exterior surfaces of the devices.

These and other objects of the present invention are achieved by a heating element for a hair styling device, including an electrically insulating inner ceramic layer, an electrically conductive resistive heating layer disposed on and in contact with the inner layer, and an electrically insulating outer ceramic layer disposed on and in contact with the resistive heating layer. There is also provided a method for manufacturing the heating element. There is further provided a hair setting device for curling hair including the heating element and a cylindrical barrel surrounding the heating element.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1A is a side cross-sectional view of a prior art hair setting device, particularly a rope heater. FIG. 1B is a front cross-sectional view of a prior art positive temperature coefficient (PTC) hair setting element.

FIG. 2 is a side cross-sectional view of a heating unit for use in a hair setting device or system according to the present invention.

FIG. 3 is a front cross sectional view of the heating unit of FIG. 2.

FIG. 4 is a side cross-sectional view of a curling iron incorporating the heating unit of FIG. 2.

FIG. 5 is a side cross-sectional view of another embodiment of a curling iron incorporating the heating unit of FIG. 2.

FIG. 6 is a front cross sectional view of the curling iron of FIG. 5.

FIGS. 7A through 7E are front cross sectional views of a barrel of the curling iron of FIG. 5.

FIG. 8 is a circuit diagram of an exemplary electrical setup of the curling iron of FIG. 3.

FIG. 9 is a circuit diagram of an exemplary control device.

FIG. 10 is a top and side view of a hair roller and hair setting assembly utilizing the heating unit of FIG. 2.

DESCRIPTION OF THE INVENTION

Referring to the drawings and, in particular, to FIG. 2, there is provided an embodiment of an electric heating unit for use as a hair curler/setter or for use in a hair styling device. Heating unit 200 includes a resistive heating conductive layer 205 sandwiched between an outer ceramic layer 210 and an inner ceramic layer 215, end gaps 220 and electrical leads 225. Electrical leads or wires 225 are electrically connected to conductive layer 205.

End gaps 220 are located at the ends of heating unit 200 due to an extension of outer ceramic layer 210 relative to conductive layer 205 and inner ceramic layer 215. In the embodiment shown in FIG. 2, outer ceramic layer 210 has a length along an axis 230 that is longer than a length along axis 230 of conductive layer 205 and inner ceramic layer 215.

In a preferred embodiment, end gaps 220 are filled with a thermally insulating adhesive material, such as an epoxy or a glue. The adhesive material contacts and bonds outer ceramic layer 210 with inner ceramic layer 215, and is both electrically and thermally insulating to act as a safety feature to prevent the ends of heating unit 200 from heating up.

Preferably, conductive layer 205 is in the form of a conductive film that is deposited on an exterior surface of inner ceramic layer 215, and may be adhered to inner ceramic base. The film is an electrically conductive film having a resistance sufficient to produce a desired amount of heat upon application of a selected current. Heating unit 200, due to the ceramic material, emits far infrared radiation upon heating. In an alternative embodiment, electrodes may be adhered to or formed in conductive layer 205 to facilitate connection with leads 225.

In a preferred embodiment, the film forming conductive layer 205 is applied as an even layer to all or substantially all of the exterior surface of inner ceramic layer 215. Outer ceramic layer 210 is then applied to conductive layer 205 so that at least a substantial portion of an interior surface of outer ceramic layer 210 is in contact with conductive layer 205. In the embodiment shown in FIG. 2, all of the interior surface of outer ceramic layer 210 is in contact with conductive layer 205 except for those portions of the interior surface of outer ceramic layer 210 that are exposed to end gap 220.

When power is switched on, conductive layer 205 will be heated first, and then ceramic layers 210 and 215 are heated directly and evenly due to their direct contact with conductive layer 205, and will emit far infrared radiation at high temperature.

A thickness of the combination of outer ceramic layer 210, conductive layer 205, and inner ceramic layer 215 is between about 1.0 mm and about 8.0 mm. In a preferred embodiment, conductive layer 205 has a thickness between about 0.1 mm and about 0.5 mm.

In another embodiment, the ceramic material contains aluminum oxide (Al₂O₃) ceramic material. Conductive layer 205 may contain any of a number of compositions such as germanium, borosilicate, ytterbium oxide, a semiconductor ceramic far-infrared material, and bismuth oxide. Preferably, conductive layer 205 does not contain any potentially harmful substances such as lead, mercury, hexavalent chromium, polyether, benzene, and benzoic acid.

In another preferred embodiment, the resistive heating film is made from a slurry that is adhered to either inner ceramic layer 215 or outer ceramic layer 210 by sintering. The expansion coefficient of the slurry is preferably substantially the same as that of the material of inner ceramic layer 215 and outer ceramic layer 210.

In a corresponding preferred method for manufacturing heating element 200, the slurry is first applied to the selected surfaces of inner ceramic layer 215 or outer ceramic layer 210, preferably by spraying.

After applied onto the selected surfaces, the slurry is sintered on the surfaces at a temperature of, e.g., about 1300° C., to form a uniform resistive heating film. In an alternative embodiment, electrodes may be applied to conductive layer 205 by applying additional slurry on the surface of the resistive heating film together with welding leads for electric connections. The additional slurry is then sintered at a high temperature, such as 1300° C., to firmly fix the electrodes to the resistive heating film.

Referring to FIG. 4, a preferred embodiment of a hair curling iron 400 includes heating unit 200, a thermally conducting cylindrical barrel 405, a handle 410, and a clamp 415. Curling iron 400 incorporates heating unit 200, which is inside thermally conducting barrel 405. Heating unit 200 is inserted into barrel 405 to produce a tight fit, so that barrel 405 surrounds heating unit 200, and so that all of the exterior surface of outer ceramic layer 210 is in contact with a portion of an interior surface of barrel 405. In one embodiment, barrel 405 is press fit onto heating unit 200. Barrel 405 is preferably made from a metal such as aluminum, or a high temperature plastic.

Handle 410 is attached to barrel 405, and leads 225 extend through barrel 405 and are connected to a power supply cord 420. Clamp 415 includes a thumb press 425, and a cylindrical portion, or “spoon”, 430.

Clamp 415 is attached to barrel 405 via a hinge and a spring mount (not shown). The hinge allows clamp 415 to be rotated to an open position, shown in FIG. 4, by pressing thumb press 425. The spring mount causes clamp 415 to rest at a closed position, where spoon 430 is substantially in contact with or partially surrounds barrel 405, when thumb press 425 is released.

Curling irons such as curling iron 400 are not limited to incorporating a single heating unit. Generally, for smaller diameter curling irons, it is preferable to use a single heating unit to maximize heat uniformity and heating time of the surface of the curling irons. For curling irons having a barrel diameter of up to 1.5 inches, a single barrel design such as curling iron 400 is preferred. For larger curling irons, such as curling irons having barrel diameters of greater than 1.5 inches, a curling iron design that utilizes multiple heating units may be preferred. Alternatively, for curling irons whose barrels are larger than the associated heating units, a single heating unit design may be utilized, as exemplified in FIGS. 7A through 7C below.

Referring to FIG. 5, a curling iron 500 is similar in design to curling iron 400, with the exception that curling iron 500 incorporates two heating units 200. Curling iron 500 includes a thermally conducting cylindrical barrel 505, a handle 510, and a clamp 515. In this embodiment, barrel 505 is shaped to accommodate both of heating units 200.

Referring to FIG. 6, barrel 505 has three sections integrally formed together to form a single piece. Barrel 505 includes a cylindrical outer portion 530, cylindrical heating unit receptacle portions 535, and a support rib portion 540. Outer portion 530 preserves the cylindrical shape of barrel 505 for hair curling. Receptacle portions 535 accommodate heating units 200 in a tight fit, so that at least substantially all of the exterior surface of each heating unit 200 is in contact with one of receptacle portions 535.

Support rib portion 540 acts as a support to prevent barrel 505 from deforming.

In another embodiment, curling iron 400 or curling iron 500 includes a thermal sensor 545 in contact with heating unit 200, for example between barrel 505 and heating unit 200. Thermal sensor 545 is electrically in contact with controls and/or indicators located, for example, in handle 510.

The thermal sensor may be connected to a control device, preferably in handle 510. The control device, which preferably includes a processor, receives temperature information, and indicates a temperature of heating unit 200. The control device may be set to indicate when a selected temperature has been reached, or may be set to discontinue power to heating unit 200 when heating unit 200 has reached a selected temperature.

Referring to FIGS. 7A through 7E, additional configurations of barrel 505 are demonstrated. FIGS. 7A, 7B and 7C show various alternative configurations of barrel 505 housing a single heating unit, in the event that heating unit 200 is smaller than the diameter of barrel 505.

FIG. 7D is similar to the configuration of barrel 505 shown in FIG. 6.

FIG. 7E shows a configuration of barrel 505 that accommodates three heating without the use of support ribs 540. In all of the above embodiments, heat transfer time is decreased, as at least substantially all of the exterior surfaces of heating units 200 directly contact a portion of barrel 505.

Although the heating unit and hair curling/setting devices described in the above embodiments are cylindrical in shape, the invention is not limited as such. Any suitable shape may be employed, such as a square tube, a triangular tube and a flat sheet. Other shapes are contemplated that would be suitable for providing heated surfaces for hair straightening or crimping.

FIGS. 8 and 9 are circuit diagrams showing embodiments of the electrical setup of curling iron 400, and of an indicator setup that may be incorporated in curling iron 400. Referring to FIG. 8, a circuit 800 shows how electrical power is transmitted to heating unit 200. Circuit 800 includes resistive element R1, which represents conductive heating layer 205. Capacitor C1 is provided to reduce noise, and capacitors C2 and C3 are provided as filters.

Referring to FIG. 9, circuit 900 shows an example of a control device used to indicate a temperature of heating unit 200. The control device is preferably incorporated into handle 410 of curling iron 400, and provides indications of the temperature of heating unit 200 and/or the barrel of curling iron 400. Such indicators notify a user when curling iron 400 is ready for use, provide an indication of time remaining until curling iron 400 is ready, and also act as a safety feature so a user will know that curling iron 400 is hot. Circuit 900 includes a processor chip 905 connected to a thermal sensor 910, multiple light-emitting diodes (LEDs) D5-D10, and switches 915 for setting temperatures of LEDs D5-D10. As heating unit 200 heats up, processor 905 directs the activation of one or more LEDs D5-D10.

For example, LEDs D5-D10 may each represent a different temperature gradation. When heating unit 200 initially begins heating, processor 905 may direct D5 to flash until a first temperature is reached. After the first temperature is reached, D5 remains steadily on, and D6 begins flashing until a second temperature is reached. This process is continued until all of LEDs D5-D10 are steadily on, indicating that curling iron 400 is ready for use. This description is purely exemplary, as any number of LEDs may be utilized and configured to alert a user to various temperatures or operating conditions.

In an alternative embodiment, heating unit 200 is incorporated as one of a plurality of heating units as a part of a hair curling system. Each heating unit is fitted with a thermally conductive sleeve. Each of the plurality of heating units may be removably connected to a power source connected to a hair curling device, and separately applied to a user's hair. The device may serve as both a port to store the heating units, and also as an electrical plug-type port to heat the units.

Referring to FIG. 10, a hair roller 1000 includes a heating unit 200 attached to a plastic insulator 1010. Heating unit 200 includes a resistive heating conductive layer 205 sandwiched between an outer ceramic layer 210 and an inner ceramic layer 215, an end gaps 220 and electrical contact wires 225.

A hair setter assembly 1020 incorporates multiple hair rollers 1000, and includes a setter cover 1030, a setter base 1040, and a power grid 1050 connected to a power cord 1060. Setter base 1040 is constructed to provide a base to removably accommodate each roller 1000 for both heating and storage. Contact wires 225 are constructed to specifically connect with power grid 1050, so the user may selectively plug in individual hair rollers 1000 for heating and remove for use. Cover 1030 is typically in a clear plastic. Plastic insulator 1010 allows the user to easily remove each hair roller 1000.

The use of heating units 200 in a hair setter assembly provides numerous advantages over the prior art, including quick heating, far infrared emission, and an inherent thermal mass. Prior are setter assemblies required that each roller have a bulky mass to retain heat for curling. Setter assemblies described above have an inherent thermal mass to retain heat due to the ceramic layers, eliminating the need for large masses of material required in prior art assemblies. Furthermore, the improved heating time allows a user to re-use individual curlers during hair setting. Therefore, for example, a 7-roller setter can be used to curl hair like a prior art 12-roller setter.

In an alternative embodiment, the heating unit is provided as a flat sheet, having a conductor sandwiched between two ceramic layers, that is flexible to be able to wrap around hair or wrap hair in a spiral configuration. In this alternative embodiment, so-called “flexible ceramics” or flexible ceramic hybrid materials may be utilized. The heating unit may also be utilized as a flat plate, e.g., to serve a hair straightening function.

The heating element of the present invention has numerous advantages, including the physical properties of uniform heat generation and far infrared emission after heated. The heated ceramic base can directly emit strong far infrared that has a potential therapeutic function.

The heating element of the present invention also provides superior watt density without sacrificing structural integrity or requiring additional conductive components. In prior art curling irons that utilize resistance wire coils, wires must be decreased in thickness, i.e., gauge, to increase watt density. Such curling irons having very thin wires present an increased risk that the wires would fail, and are also complex to manufacture. Curling irons utilizing PTC pellets require additional die cast components to conduct heat. The heating units of the present invention provide thin conductive films having high film density without the risk of failure, the increased number of components, or the complexity of prior art devices.

Because the conductive surface heating film is preferably sintered onto the ceramic base after the resistance slurry material is sprayed on surface of the ceramic base, the film is uniform, thus resulting in even temperature distribution and long service life. Also, the conductive film heats uniformly, resulting in a uniform heating of the ceramic layers and the outer barrel of the hair curler or curling iron. Furthermore, because the conductive material contacts at least a substantial portion of the surfaces of the ceramic layers, the time required to heat the ceramic layers, and thus the hair curler or curling iron, is reduced.

It should be understood that various alternatives, combinations and modifications of the teachings described herein could be devised by those skilled in the art. The present invention is intended to embrace all such alternatives, modifications and variances that fall within the scope of the appended claims. 

1. A heating element for a hair styling device, comprising: an electrically insulating inner ceramic layer; an electrically conductive resistive heating layer disposed on and in contact with said inner layer; and an electrically insulating outer ceramic layer disposed on and in contact with said resistive heating layer.
 2. The heating element of claim 1, further comprising lead wires electrically connected to said resistive heating layer.
 3. The heating element of claim 1, wherein said inner core is bonded to said outer core by a high temperature, thermally insulating adhesive material.
 4. The heating element of claim 1, wherein said inner ceramic layer and said outer ceramic layer are made from aluminum oxide (Al₂O₃) ceramics.
 5. The heating element of claim 1, wherein said heating element is a cylindrical tube having an axis.
 6. The heating element of claim 5, wherein a combination of a thickness of said outer ceramic layer, a thickness of said resistive heating layer, and a thickness of said inner ceramic layer is between about 1.0 mm and about 8.0 mm.
 7. The heating element of claim 1, wherein said heating element emits far infrared radiation when heated to a selected temperature.
 8. The heating element of claim 5, wherein said outer ceramic layer has a length along said axis that is longer than a length along said axis of said resistive heating layer and said inner ceramic layer.
 9. The heating element of claim 1, wherein said resistive heating layer has a thickness of between about 0.1 mm and about 0.3 mm.
 10. A hair setting device for curling hair, comprising: a cylindrical heating element having an electrically insulating inner ceramic layer, an electrically conductive resistive heating layer disposed on and in contact with said inner layer, and an electrically insulating outer ceramic layer disposed on and in contact with said resistive heating layer; and a cylindrical barrel surrounding said heating element.
 11. The hair setting device of claim 10, wherein said cylindrical heating element is tightly fit into said barrel so that said outer ceramic layer is in contact with an interior surface of said barrel.
 12. The hair setting device of claim 10, wherein said barrel is made from a material selected from the group consisting of: a heat conductive metal and a high temperature plastic.
 13. The hair setting device of claim 10, further comprising a thermal sensor in thermal contact with said heating element and connected to a control device.
 14. The hair setting device of claim 13, wherein said thermal sensor is positioned between said barrel and said heating element.
 15. The hair setting device of claim 10, further comprising: a handle attached to an end of said barrel; a partially cylindrically shaped clamp having a cylindrical portion and a thumb press, wherein said clamp is attached to said barrel via a hinge and a spring mount.
 16. The hair setting device of claim 10, wherein said cylindrical heating element is a plurality of cylindrical heating elements electrically connected to a control device.
 17. A method for manufacturing a heating element for a hair setting device, comprising the steps of: depositing an electrically conductive heating film on at least a portion of a surface of an inner cylindrical ceramic base to form a resistive heating layer; connecting said heating film to electrically conductive wire leads; and disposing an outer cylindrical ceramic layer on said resistive heating layer.
 18. The method of claim 17, further comprising the step of adhering said film to said surface by sintering.
 19. The method of claim 17, wherein said step of depositing is accomplished by spraying a slurry of conductive material to said surface.
 20. The method of claim 17, further comprising: bonding said inner cylindrical ceramic layer to said outer cylindrical ceramic layer by applying high temperature thermally insulating adhesive material to said inner ceramic layer and to said outer ceramic layer. 